We have previously investigated the regulation of M-CSF production from human monocytes induced by various cytokines. The results of these studies have been submitted for publication. We are currently expanding this work and have examined the ability of antibodies to the surface antigens: CD44, CD45 and LFA-3 to stimulate M-CSF production. Immobilized antibodies to all three antigens were able to induce M-CSF mRNA while antibodies to other surface proteins did not. F(ab)2 fragments of a CD44 antibody were used to demonstrate that this process did not require Fc binding. Although these same antibodies also induced some measurable M- CSF release, LPS greatly augmented the M-CSF production when added to the cultures. LPS alone was not able to stimulate M-CSF protein release or message. In addition, we found that IL-1beta could be used in the place of the LPS. These results have been submitted for publication. We are currently investigating the role of IL-1-beta in regulating both the transcription and translation of CD44-induced M-CSF production by human monocytes.